This machine is very similar to preforming machine, except that it is performed on one side of a rotating flat disk known as a lap, and it is used especially to create flat surfaces on a stone. Laps are often made of cast iron, steel, or a copper-bronze alloy, but other materials can also be used.

FACETING

Faceting is most often done on transparent stones. Flat facets are cut over the entire surface of the stone, usually in a highly symmetrical pattern. The stone is doped (usually with adhesive wax, epoxy, or cyanoacrylate glue) on a metal dopstick, which is then inserted in a faceter that allows precise control of positioning. The cutting angle is adjusted vertically via a protractor and rotationally via an index gear. Faceter rests on a height adjustable table and distance between lap and table is easy adjusted by eccentric movement of the table. The table is easy raised or lowered by micrometer dial to allow the operator accurate control of the cutting depth. The facets are then ground, sanded on a rotating lap, while water or another liquid acts as a coolant and lubricant. When one side (top or bottom) of the stone is finished, a jig is used to transfer the stone to a dopstick on the opposite side.

POLISHING

After a gemstone is sawed and ground to the desired shape and sanded to remove rough marks left by coarser grits, it is usually polished to a mirror-like finish to aid light reflection from the surface of the stone (or refraction through the stone, in the case of transparent materials). Polishing removes small quantities of stone and can be used, especially when faceting small stones,to do ultra-fine shaping of the stone.